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SubjectRe: /proc/sys/kernel/pid_max issues
On Mon, 2004-09-13 at 03:42, William Lee Irwin III wrote:
>> The resource tracking and locking implications of this are disturbing.
>> Would fully pseudorandom allocation be acceptable?

On Mon, Sep 13, 2004 at 10:11:29AM -0400, Albert Cahalan wrote:
> There's no point.
> LRU reduces accidents that don't involve an attacker.
> Strong crypto random can make some attacks a bit harder.
> OpenBSD does this. It doesn't work well enough to bother
> with if the implementation is problematic; there's not
> much you can do while avoiding 64-bit or 128-bit PIDs.
> Pseudorandom is 100% useless.
> Per-user PID recycling would make it much harder for
> an attacker to grab a specific PID. Perhaps the attacker
> knows that a sched_setscheduler call is coming, and he
> has a way to make the right process restart or crash.
> Normally, this lets him get SCHED_FIFO or somesuch.
> With per-user PID recycling, it would be difficult for
> him to grab the desired PID.

I'd suggest pushing for 64-bit+ pid's, then. IIRC most of the work
there is in userspace (the in-kernel part is trivial).

-- wli
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